Polymer composition and film thereof

ABSTRACT

Disclosed is a polymer composition comprising a copolymer of propylene, a specific amount of α-olefin having 4 or more carbon atoms and optionally a specific amount of ethylene and a specific 1-butene homopolymer or copolymer having a melting point of not lower than 60° C. but lower than 125° C., wherein the polymer composition contains a 20° C. xylene-soluble portion of the polymer composition in an amount of from 5 to 45% by weight and the 20° C. xylene-soluble portion has an intrinsic viscosity of 1.3 dl/g or higher. The polymer composition may optionally contain a specific propylene copolymer and/or a specific propylene homopolymer or copolymer having a melting point of from 150° C. to 170° C.

This is a divisional application of application Ser. No. 10/920,274filed Aug. 18, 2004, which claims priority under 35 U.S.C. §119 toJapanese Patent Applications Nos. 2003-208001 and 2003-208002, bothfiled on Aug. 20, 2003. The entire disclosures of the priorapplications, U.S. application Ser. No. 10/920,274 and Japanese PatentApplications Nos. 2003-208001 and 2003-208002, are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to polymer compositions and to theirfilms. Particularly, the invention relates to polymer compositions fromwhich films superior in low-temperature heat sealability, hot tackproperty and transparency can be produced and also relates to theirfilms. In addition, the invention relates to polymer compositions fromwhich films superior in low-temperature heat sealability, hot tackproperty and transparency can be obtained and which exhibit lesstackiness when being fabricated into films and the invention alsorelates to their films.

2. Description of the Related Art

Films or sheets obtained by shaping polypropylene have been used widelyin the field, particularly, of packaging of foods or the like due totheir superior transparency, heat resistance, food sanitation and thelike.

JP-A-55-59964 discloses a film that has a lowered heat seal temperatureand an increased heat seal strength and that is not affected withrespect to other properties films are required to possess. Specificallydisclosed is a polypropylene multilayer film in which a layer of amixture composed of from 85 to 97 parts by weight of apropylene-butene-1 copolymer having a butene-1 content of from 10 to 25%by weight and from 3 to 15 parts by weight of a propylene-butene-1copolymer having a butene-1 content of from 80 to 93%.

JP-A-61-108647 discloses a crystalline propylene random copolymercomposition from which a polypropylene composite laminate superior inlow-temperature heat sealability and heat seal strength can be obtained.Specifically disclosed is a crystalline propylene random copolymercomposition comprising a crystalline propylene random copolymer which ismade up of propylene and α-olefin other than propylene and whichcontains the propylene as a main component and a 1-butene randomcopolymer made up of ethylene and 1-butene.

In recent years, in the field of packaging of foods and the like, thefabrication speed of bags has been increased and a material which can beprocessed at an increased fabrication speed is awaited. For thepropylene copolymer compositions, a further improvement inlow-temperature heat sealability, hot tack property and transparency offilms obtained from the compositions is awaited. Moreover, animprovement in tackiness of the compositions during film formation isalso awaited.

SUMMARY OF THE INVENTION

An object of the present is to provide a polymer composition from whicha film superior in low-temperature heat sealability, hot tack propertyand transparency can be afforded and to provide a film thereof. Anotherobject of the present invention is to provide a polymer composition fromwhich films superior in low-temperature heat sealability, hot tackproperty and transparency can be obtained and which exhibit lesstackiness when being fabricated into films and to provide a filmthereof.

In a first embodiment, the present invention is directed to a polymercomposition comprising:

from 70 to 99% by weight of a polymer (A) satisfying Requirements (A-1)through (A-3) defined below and

from 1 to 30% by weight of a polymer (B) satisfying Requirements (B-1)and (B-2) defined below, the polymer composition satisfying Requirements(1) and (2) defined below, wherein said amounts of the polymers (A) and(B) are based on a combined amount of the polymers (A) and (B):

Requirement (1): the content of a 20° C. xylene-soluble portion of thepolymer composition is from 5 to 45% by weight,

Requirement (2): a 20° C. xylene-soluble portion of the polymercomposition has an intrinsic viscosity of 1.3 dl/g or higher,

Requirement (A-1): the polymer is a copolymer of propylene and α-olefinhaving 4 or more carbon atoms or a copolymer of propylene, α-olefinhaving 4 or more carbon atoms and ethylene,

Requirement (A-2): the polymer has a content of structural units derivedfrom α-olefin having 4 or more carbon atoms of from 3 to 40% by weight,

Requirement (A-3): the polymer has a content of structural units derivedfrom ethylene of from 0.1 to 5% by weight when the polymer is acopolymer of propylene, α-olefin having 4 or more carbon atoms andethylene,

Requirement (B-1): the polymer is a homopolymer of 1-butene, a copolymerof 1-butene and ethylene, a copolymer of 1-butene and propylene, acopolymer of 1-butene and α-olefin having 4 or more carbon atoms otherthan 1-butene, a copolymer of 1-butene, ethylene and propylene or acopolymer of 1-butene, ethylene and α-olefin having 4 or more carbonatoms other than 1-butene, and

Requirement (B-2): the polymer has a melting point of not lower than 60°C. but lower than 125° C.

In a second embodiment, the present invention is directed to a polymercomposition according to the first embodiment, wherein the polymercomposition further comprises from 1 to 25 parts by weight, based on 100parts by weight of the polymers (A) and (B) in total, of a polymer (D)satisfying Requirements (D-1), (D-2) and (D-3) defined below:

Requirement (D-1): the polymer is a homopolymer of propylene, acopolymer of propylene and ethylene, or a copolymer of propylene andα-olefin having 4 or more carbon atoms,

Requirement (D-2): the polymer has a melting point of from 150° C. to170° C., and

Requirement (D-3): the polymer has a content of structural units derivedfrom ethylene of from 0.1 to 3% by weight when the polymer is acopolymer of propylene and ethylene or the polymer has a content ofstructural units derived from α-olefin having 4 or more carbon atoms offrom 0.1 to 3% by weight when the polymer is a copolymer of propyleneand α-olefin having 4 or more carbon atoms.

In a third embodiment, the present invention is directed to a polymercomposition comprising:

from 30 to 98% by weight of a polymer (A) satisfying Requirements (A-1)through (A-3) defined above,

from 1 to 30% by weight of a polymer (B) satisfying Requirements (B-1)and (B-2) defined above, and

from 1 to 50% by weight of a polymer (C) satisfying Requirements (C-1)through (C-5) defined below, the polymer composition satisfyingRequirements (1) and (2) defined above, wherein said amounts of thepolymers (A), (B) and (C) are based on a combined amount of the polymers(A), (B) and (C):

Requirement (C-1): the polymer is a copolymer of propylene and ethylene,a copolymer propylene and α-olefin having 4 or more carbon atoms, or acopolymer of propylene, ethylene and α-olefin having 4 or more carbonatoms,

Requirement (C-2): the polymer has a content of structural units derivedfrom ethylene of from 0.1 to 10% by weight when the polymer is acopolymer of propylene and ethylene or a copolymer of propylene,ethylene and α-olefin having 4 or more carbon atom, wherein this contentis based on the weight of the polymer,

Requirement (C-3): the polymer has a content of structural units derivedfrom α-olefin having 4 or more carbon atoms of from 0.1 to 10% by weightwhen the polymer is a propylene and α-olefin having 4 or more carbonatoms or a copolymer of propylene, ethylene and α-olefin having 4 ormore carbon atoms,

Requirement (C-4): the polymer has a content, based on the weight of thepolymer, of structural units derived from α-olefin having 4 or morecarbon atoms less than that of polymer (A) when the polymer is acopolymer of propylene and α-olefin having 4 or more carbon atoms or acopolymer of propylene, ethylene and α-olefin having 4 or more carbonatoms, and

Requirement (C-5): the polymer has a melting point of not lower than125° C. but lower than 150° C.

In a fourth embodiment, the present invention is directed to a polymercomposition according to the third embodiment, wherein the polymercomposition further comprises from 1 to 25 parts by weight, based on 100parts by weight of the polymers (A), (B) and (C) in total, of a polymer(D) satisfying Requirements (D-1), (D-2) and (D-3) defined above.

In the polymer compositions of the first through fourth embodiments, thepolymer (A) is a copolymer of propylene and 1-butene.

In the polymer compositions of the third and fourth embodiments, thepolymer (C) is a copolymer of propylene and ethylene or a copolymer ofpropylene, ethylene and 1-butene.

In the polymer compositions of the second and fourth embodiments, thepolymer (D) is a homopolymer of propylene having a melting point of from155° C. to 170° C.

Moreover, the present invention also provides a film having at least onelayer made of any of the polymer compositions mentioned above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polymer composition of the first embodiment of the present inventionis a polymer composition comprising from 70 to 99% by weight of thepolymer (A) and from 1 to 30% by weight of the polymer (B), the polymercomposition satisfying Requirements (1) and (2) defined below, whereinsaid amounts of the polymers (A) and (B) are based on a combined amountof the polymers (A) and (B):

Requirement (1): the content of a 20° C. xylene-soluble portion of thepolymer composition is from 5 to 45% by weight, and

Requirement (2): a 20° C. xylene-soluble portion recovered from thepolymer composition has an intrinsic viscosity of 1.3 dl/g or higher.

The polymer composition of the second embodiment of the presentinvention is a polymer composition of the first embodiment which furthercomprises from 1 to 25 parts by weight, based on 100 parts by weight ofthe polymers (A) and (B) in total, of the polymer (D).

The polymer composition of the third embodiment of the present inventionis a polymer composition comprising from 30 to 98% by weight of thepolymer (A), from 1 to 30% by weight of the polymer (B), and from 1 to50% by weight of the polymer (C), the polymer composition satisfyingRequirements (1) and (2) defined above, wherein said amounts of thepolymers (A), (B) and (C) are based on a combined amount of the polymers(A), (B) and (C).

The polymer composition of the fourth embodiment of the presentinvention is a polymer composition of the third embodiment which furthercomprises from 1 to 25 parts by weight, based on 100 parts by weight ofthe polymers (A), (B) and (C) in total, of the polymer (D).

The content of a 20° C. xylene-soluble portion (henceforth, referred toas CXS) of the polymer compositions of the present invention is from 5to 45% by weight (Requirement (1)) and, from the viewpoints ofpreventing polymer compositions from exhibiting tackiness during theirfilm formation and low-temperature heat sealability of resulting films,preferably is from 10 to 40% by weight.

In the polymer compositions of the present invention, the intrinsicviscosity of the CXS (henceforth, referred to as [η]CXS) is 1.3 dl/g orhigher (Requirement (2)), preferably from 1.3 to 7 dl/g and, from theviewpoint of hot tack strength, is more preferably from 1.34 to 7 dl/g,particularly preferably from 1.38 to 5 dl/g. It should be noted that the[η]CXS in the present invention is measured in tetralin at 135° C. Forthe measurement, an Ubbelohde's viscometer is used.

The melt flow rate (MFR), measured at 230° C., of the polymercompositions of the present invention is, from the viewpoints offluidity and film formability, usually from 0.1 to 50 g/10 minutes,preferably from 1 to 20 g/10 minutes, more preferably from 3 to 15 g/10minutes, and even more preferably from 4 to 15 g/10 minutes.

In the polymer compositions of the first and second embodiments of thepresent invention, the content of the polymer (A) and that of thepolymer (B) are from 70 to 99% by weight and from 1 to 30% by weight,respectively and, from the viewpoint of preventing polymer compositionsfrom exhibiting tackiness during their film formation, preferably from75 to 99% by weight and from 1 to 25% by weight, respectively and morepreferably from 80 to 97% by weight and from 3 to 20% by weight,respectively.

In the polymer compositions of the third and fourth embodiments of thepresent invention, the content of the polymer (A), that of the polymer(B) and that of the polymer (C) are from 30 to 98% by weight, from 1 to30% by weight and from 1 to 50% by weight, respectively and, from theviewpoints of preventing polymer compositions from exhibiting tackinessduring their film formation and low-temperature heat sealability ofresulting films, preferably from 40 to 98% by weight, from 1 to 25% byweight and from 1 to 45% by weight, respectively and more preferablyfrom 50 to 96% by weight, 3 to 20% by weight and from 1 to 40% byweight, respectively.

The polymer (A) used in the present invention is a copolymer ofpropylene and α-olefin having 4 or more carbon atoms or a copolymer ofpropylene, α-olefin having 4 or more carbon atoms and ethylene(Requirement (A-1)).

The content of structural units derived from α-olefin having 4 or morecarbon atoms is from 3 to 40% by weight (Requirement (A-2)). From theviewpoints of preventing polymer compositions from exhibiting tackinessduring their film formation and low-temperature heat sealability ofresulting films, the content is preferably from 5 to 40% by weight, morepreferably from 10 to 30% by weight, and even more preferably from 15 to40% by weight. It should be noted that said contents are based on thecombined weight of the structural units derived from propylene and thestructural units derived from α-olefin having 4 or more carbon atoms inthe polymer (A).

When the polymer (A) is a copolymer of propylene, α-olefin having 4 ormore carbon atoms and ethylene, the content of structural units derivedfrom ethylene is 0.1 to 5% by weight (Requirement (A-3)). From theviewpoints of preventing polymer compositions from exhibiting tackinessduring their film formation and preventing films from whitening withtime, the content is preferably up to 3% by weight. It should be notedthat said contents are based on the total of the combined weight of thestructural units derived from propylene, the structural units derivedfrom ethylene and the structural units derived from α-olefin having 4 ormore carbon atoms in the polymer (A).

The melt flow rate (MFR), measured at 230° C., of the polymer (A) isusually from 0.1 to 50 g/10 minutes and, from the viewpoint of fluidity,it is preferably from 1 to 20 g/10 minutes, more preferably from 3 to 15g/10 minutes and even more preferably from 4 to 15 g/10 minutes.

It is possible to control the fluidity of the polymer (A) by changingits molecular weight by a conventional method. For example, it ispossible to control the MFR of the polymer (A) by melt kneading it inthe presence of an organic peroxide.

The α-olefin having 4 or more carbon atoms to be used for thepreparation of the polymer (A) is preferably an α-olefin having from 4to 20 carbon atoms and more preferably is an α-olefin having from 4 to12 carbon atoms.

Examples of the α-olefin having 4 or more carbon atoms to be used forthe preparation of the polymer (A) include 1-butene, 2-methyl-1-propene,1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene,2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene,3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene,1-heptene, 2-methyl-1-hexene, 2,3,-dimethyl-1-pentene,2-ethyl-1-pentene, 2,3,4-trimethyl-1-butene, 2-methyl-3-ethyl-1-butene,1-octene, 5-methyl-1-pentene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene,2-propyl-1-heptene, 2-methyl-3-ethyl-1-heptene,2,3,4-trimethyl-1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene,1-nonene, 1-decene, 1-undecene and 1-dodecene.

Preferred are 1-butene, 1-pentene, 1-hexene and 1-octene. From theviewpoint of copolymerizability and the economical standpoint, morepreferred are 1-butene and 1-hexene.

Examples of the polymer (A) includes a propylene-1-butene copolymer, apropylene-1-hexene copolymer, a propylene-ethylene-1-butene copolymerand a propylene-ethylene-1-hexene copolymer. Preferred are apropylene-1-butene copolymer and a propylene-1-hexene copolymer.

The polymer (A) is preferably a polymer containing from 1 to 30% byweight of a segment (a-1) defined below and from 70 to 99% by weight ofa segment (a-2) defined below, wherein said amounts of the segments arebased on the combined weight of the segments:

segment (a-1): a segment having structural units derived from 1-butenein a content of not less than 1% by weight but less than 15% by weight,

segment (a-2): a segment having structural units derived from 1-butenein a content of not less than 15% by weight but not more than 40% byweight.

From the viewpoint of properties of a powder during polymerization andalso from the viewpoints of preventing polymer compositions fromexhibiting tackiness during their film formation and low-temperatureheat sealability of resulting films, the content of the segment (a-1)and that of the segment (a-2) are preferably from 1 to 20% by weight andfrom 80 to 99% by weight, respectively. The content of 1-butene in thesegment (a-1) is preferably from 1 to 10% by weight. The content of1-butene in the segment (a-2) is preferably from 15 to 30% by weight.

Examples of the segment (a-1) include a propylene-1-butene copolymersegment and a propylene-ethylene-1-butene copolymer segment. Preferredis a propylene-1-butene copolymer segment. Examples of the segment (a-2)also include a propylene-1-butene copolymer segment and apropylene-ethylene-1-butene copolymer segment. Preferred is apropylene-1-butene copolymer segment. The kinds of the structural unitsof the segment (a-1) and those of the structural units of the segment(a-2) may be either identical or different.

Examples of such a polymer (A) containing a segment (a-1) and a segment(a-2) include a (propylene-1-butene)-(propylene-1-butene) copolymer, a(proppylene-1-butene)-(propylene-ethylene-1-butene) copolymer, a(propylene-ethylene-1-butene)-(propylene-1-butene) copolymer, and a(propylene-ethylene-1-butene)-(propylene-ethylene-1-butene) copolymer.Preferred are a (propylene-1-butene)-(propylene-1-butene) copolymer anda (propylene-1-butene)-(propylene-1-butene) copolymer. More preferred isa (propylene-1-butene)-(propylene-1-butene) copolymer.

The polymer (B) to be used in the present invention is a homopolymer of1-butene, a copolymer of 1-butene and ethylene, a copolymer of 1-buteneand propylene, a copolymer of 1-butene and α-olefin having 4 or morecarbon atoms other than 1-butene, a copolymer of 1-butene, ethylene andpropylene, or a copolymer of 1-butene, ethylene and α-olefin having 4 ormore carbon atoms other than 1-butene (Requirement (B-1)).

When the polymer (B) is a copolymer of 1-butene and α-olefin having 4 ormore carbon atoms other than 1-butene, examples of the α-olefin include1-pentene and 1-hexene.

When the polymer (B) is a copolymer of 1-butene and α-olefin having 4 ormore carbon atoms other than 1-butene, examples of such a copolymerinclude a 1-butene-propylene copolymer, a 1-butene-ethylene copolymerand a 1-butene-propylene-ethylene copolymer. Preferred are a1-butene-ethylene copolymer and a 1-butene-propylene copolymer.

When the polymer (B) is a copolymer, its content of structural unitsderived from 1-butene is usually from 55 to 99.9% by weight. From theviewpoint of preventing polymer compositions from exhibiting tackinessduring their film formation, the content is preferably from 60 to 99.9%by weight and more preferably from 65 to 99.9% by weight.

When the polymer (B) is a copolymer, its content of structural unitsderived from monomers other than 1-butene is usually from 0.1 to 45% byweight, preferably from 0.1 to 40% by weight, and more preferably from0.1 to 35% by weight.

The melting point (Tm) of the polymer (B) is not lower than 60° C. butlower than 125° C. (Requirement (B-2)). From the viewpoints ofpreventing polymer compositions from exhibiting tackiness during theirfilm formation and low-temperature heat sealability of resulting films,the melting point is preferably from 65 to 120° C. and more preferablyfrom 65 to 115° C.

The intrinsic viscosity [η] of the polymer (B) is preferably from 1.4 to7 dl/g, more preferably from 1.5 to 6 dl/g and even more preferably from1.6 to 5 dl/g from the viewpoints of hot tack strength of films anddispersibility of the polymer achieved during the pelletization of thecomposition.

The polymer (C) used in the present invention is a copolymer ofpropylene and ethylene, a copolymer propylene and α-olefin having 4 ormore carbon atoms, or a copolymer of propylene, ethylene and α-olefinhaving 4 or more carbon atoms (Requirement (C-1)).

When the polymer (C) is a copolymer of propylene and ethylene or acopolymer of propylene, ethylene and α-olefin having 4 or more carbonatoms, the polymer has a content of structural units derived fromethylene of from 0.1 to 10% by weight (Requirement (C-2)). The contentis preferably from 0.1 to 8% by weight and more preferably from 1 to 7%by weight.

When the polymer is a copolymer of propylene and ethylene or a copolymerof propylene, ethylene and α-olefin having 4 or more carbon atoms, thepolymer must satisfy the aforementioned Requirement (C-2) from theviewpoint of properties of a powder during the polymerization for theproduction of the polymer (C) and also from the viewpoints of preventingpolymer compositions from exhibiting tackiness during their filmformation and low-temperature heat sealability of resulting films.

When the polymer (C) is a copolymer of propylene and α-olefin having 4or more carbon atoms or a copolymer of propylene, ethylene and α-olefinhaving 4 or more carbon atoms, the polymer has a content of structuralunits derived from α-olefin having 4 or more carbon atoms of from 0.1 to10% by weight (Requirement (C-3)), and preferably is from 1 to 8% byweight.

When the polymer (C) is a copolymer of propylene and α-olefin having 4or more carbon atoms or a copolymer of propylene, ethylene and α-olefinhaving 4 or more carbon atoms, the polymer (C) has a content, based onthe weight of the polymer, of structural units derived from α-olefinhaving 4 or more carbon atoms less than that of polymer (A) (Requirement(C-4)).

When the polymer (C) is a copolymer of propylene and α-olefin having 4or more carbon atoms or a copolymer of propylene, ethylene and α-olefinhaving 4 or more carbon atoms, the polymer (C) must satisfy theaforementioned Requirements (C-3) and (C-4) from the viewpoint ofproperties of a powder achieved during the polymerization for theproduction of polymer (C) and also from the viewpoints of preventingpolymer compositions from exhibiting tackiness during their filmformation and low-temperature heat sealability of resulting films.

The melting point of the polymer (C) is not lower than 125° C. but lowerthan 150° C. (Requirement (C-5)). It is preferably from not lower than125° C. but not higher than 145° C. from the viewpoint of properties ofa powder achieved during the polymerization for the production ofpolymer (C) or low-temperature heat sealability of films.

The melt flow rate (MFR), measured at 230° C., of the polymer (C) isusually from 0.1 to 200 g/10 minutes and, from the viewpoints offluidity and film formability, preferably from 1 to 150 g/10 minutes.

It is possible to control the fluidity of the polymer (C) by changingits molecular weight by a conventional method. For example, it ispossible to control the MFR of the polymer (C) by melt kneading it inthe presence of an organic peroxide.

In the polymer compositions of the first and second embodiments of thepresent invention, the content of the polymer (A) and that of thepolymer (B) are preferably from 75 to 99% by weight and from 1 to 25% byweight, respectively, and more preferably from 80 to 97% by weight andfrom 3 to 20% by weight, respectively from the viewpoint of preventingpolymer compositions from exhibiting tackiness during their filmformation.

In the polymer compositions of the third and fourth embodiments of thepresent invention, the content of the polymer (A), that of the polymer(B) and that of the polymer (C) are preferably from 40 to 98% by weight,from 1 to 25% by weight and from 1 to 45% by weight, respectively, andmore preferably from 50 to 96% by weight, from 3 to 20% by weight andfrom 1 to 40% by weight, respectively from the viewpoints of preventingpolymer compositions from exhibiting tackiness during their filmformation and low-temperature heat seal temperature of resulting films.

The polymer (D) to be used in the present invention is a homopolymer ofpropylene, a copolymer of propylene and ethylene, or a copolymer ofpropylene and α-olefin having 4 or more carbon atoms (Requirement(D-1)). From the viewpoints of preventing polymer compositions fromexhibiting tackiness during their film formation, a homopolymer ofpropylene is preferred.

The melting point of the polymer (D) is from 150° C. to 170° C.(Requirement (D-2)). From the viewpoints of preventing polymercompositions from exhibiting tackiness during their film formation, itis preferably from 155° C. to 170° C., and more preferably from 158° C.to 170° C.

When the polymer (D) is a copolymer of propylene and ethylene, thepolymer has a content of structural units derived from ethylene of from0.1 to 3% by weight and when the polymer is a copolymer of propylene andα-olefin having 4 or more carbon atoms, the polymer has a content ofstructural units derived from α-olefin having 4 or more carbon atoms offrom 0.1 to 3% by weight (Requirement (D-3)). From the viewpoints ofpreventing polymer compositions from exhibiting tackiness during theirfilm formation, it is preferably from 0.1 to 2% by weight.

The melt flow rate (MFR), measured at 230° C., of the polymer (D) isusually from 0.1 to 200 g/10 minutes and, from the viewpoints offluidity and film formability, preferably from 1 to 150 g/10 minutes.

It is possible to control the fluidity of the polymer (D) by changingits molecular weight by a conventional method. For example, it ispossible to control the MFR of the polymer (D) by melt kneading it inthe presence of an organic peroxide.

The content of the polymer (D) in a polymer composition containing nopolymer (C) is from 1 to 25 parts by weight based on 100 parts by weightof the polymers (A) and (B) in total. From the viewpoint of hot tackstrength, it is preferably from 1 to 18 parts by weight and morepreferably from 1 to 12 parts by weight. On the other hand, the contentof the polymer (D) in a polymer composition containing the polymer (C)is from 1 to 25 parts by weight based on 100 parts by weight of thepolymers (A), (B) and (C) in total.

It is possible to produce the polymers (A), (C) and (D) bypolymerizations using appropriate polymerization catalysts.

Examples of the catalyst for polymerization include Ziegler-Natta typecatalysts and metallocene-type catalysts. Preferred are catalystscontaining Ti, Mg and halogen as essential components. For example,Ti—Mg-based catalysts comprising a solid catalyst component obtained bycompounding a magnesium compound with a titanium compound, and catalystsystems comprising such a solid catalyst component, an organoaluminumcompound and a third component, e.g. an electron-donating compound, arementioned. Specific examples are catalyst systems disclosed, forexample, in JP-A-61-218606, JP-A-61-287904 and JP-A-7-216017.

Preferred examples of the organoaluminum compound includetriethylaluminum, triisobutylaluminu, a mixture of triethylaluminu anddiethylaluminum chloride, and tetraethyldialumoxane.

Preferred examples of the electron-donating compound includecyclohexyl-ethyldimethoxysilane, tert-butyl-n-propyldimethoxysilane,tert-butylethyldimethoxysilane and dicyclopentyldimethoxysilane.

Examples of the type of polymerization include solvent polymerizationusing an inert solvent typified by hydrocarbon compounds such as hexane,heptane, octane, decane, cyclohexane, methylcyclohexane, benzene,toluene and xylene; bulk polymerization using liquid monomer as solvent;and gas phase polymerization carried out in vaporous monomer. Preferredare bulk polymerization and gas phase polymerization becausepost-treatment can be conducted easily. These polymerization may becarried out either in a batch manner or in a continuous manner.

When the polymer (A) is a copolymer containing the aforementionedsegments (a-1) and (a-2), its production can be carried out by multisteppolymerization comprising a first polymerization step and apolymerization step or steps following the first polymerization step.

The type of the polymerization used in the first polymerization step andthat used in the following polymerization step or steps may be eitherthe same or different. From the viewpoints of polymerization activityand ease in post-treatment, polymerization is carried out in the absenceof inert solvent in the first polymerization step and polymerization iscarried out in a gas phase in the step or steps following the firstpolymerization step. The polymerization in the first polymerization stepand the polymerization in the step or each of the steps following thefirst polymerization step may be carried out either in the samepolymerization reactor or in different polymerization reactors.

Examples of the multistep polymerization composed of the firstpolymerization step and a polymerization step or steps following thefirs polymerization step include solvent-solvent polymerization,bulk-bulk polymerization, gas phase-gas phase polymerization,solvent-gas phase polymerization, bulk-gas phase-gas phasepolymerization, solvent-gas phase-gas phase polymerization and bulk-gasphase-gas phase polymerization. Preferred are bulk-gas phasepolymerization, gas phase-gas phase polymerization and bulk-gasphase-gas phase polymerization.

The polymerization temperature in the first polymerization step isusually from 20 to 150° C. and, from the viewpoints of productionefficiency and ease in controlling the contents of the copolymersegments (a-1) and (a-2), preferably from 35 to 95° C.

The polymerization temperature in the step or each of the stepsfollowing the first polymerization step may be equal to or differentfrom the polymerization temperature in the first polymerization step.However, it is usually from 20 to 150° C. and preferably from 35 to 95°C.

The preparation of the polymer (B) can be carried out by polymerizationusing a method widely employed in industrial production.

It is possible to produce the polymer compositions of the presentinvention by mixing ingredients prepared separately and then dispersingthem uniformly. Examples of such a method include extrusion meltblending and Banbury blending.

In the preparation of the polymer compositions of the present invention,it is desirable to melt knead each of the polymers (A), (C) and (D) ormixtures thereof in the presence of an organic peroxide. However, it isundesirable to melt knead the polymer (B) or a mixture of the polymer(B) and other polymers.

The polymer compositions of the present invention may contain additivesor a resin other than the polymers (A), (B), (C) and (D), if required.Examples of additives include antioxidants, UV absorbers, antistaticagents, lubricants, nucleating agents, adhesives, anticlouding agentsand antiblocking agents.

The resin other than the polymers (A), (B), (C) and (D) may bepolyethylene or the like.

The film of the present invention is a film having at least one layermade of any of the polymer compositions of the present inventiondescribed above. The film of the present invention may be either a filmcomposed of a single layer or a multilayer film.

The method for producing the film of the present invention may be aconventionally-used method such as the inflation method, the T diemethod and the calender method. The method for producing the multilayerfilm may be a conventionally-used method such as coextrusion, extrusionlamination, hot lamination and dry lamination.

The film of the present invention may be a drawn film. The method forproducing the drawn film may be a method in which a film or sheetprepared by processing a polymer composition of the present invention isstretched. The method of the stretching may be a method of uniaxially orbiaxially stretching a film or sheet by roll stretching, tenterstretching, tubular stretching, or the like.

The film of the present invention preferably is an undrawn film producedby coextrusion or a film produced by biaxially drawing from theviewpoints of balance between properties of the film includinglow-temperature heat sealability, transparency and rigidity.

Examples of the application of the film of the present invention includewrapping of various items. Examples of the items to be wrapped in thefilm of the present invention include foods and clothes. Foods arepreferred.

EXAMPLES

The present invention will be described specifically below withreference to examples and compatible examples. However, the invention isnot restricted to the examples. The methods for preparing the samplesused in the examples and comparative examples and the methods formeasuring physical properties are shown below.

(1) Content of Structural Units Derived from 1-butene (Unit: % byWeight)

The IR spectrum was taken by a method described in MacromoleculeHandbook (1995, published by Kinokuniya), page 619. Based on thespectrum, the content of structural units derived from 1-butene wasdetermined.

(2) Content of Structural Units Derived from ethylene (Unit: % byWeight)

By a conventional method using an infrared spectrophotometer and astandard sample, the content of structural units derived from ethylenewas determined from characteristic absorptions appearing within therange from 732 to 720 cm⁻¹.

(3) Intrinsic Viscosity ([η]; Unit: dl/g)

The intrinsic viscosity was measured at 135° C. in tetralin using anUbbelohde's viscometer.

(4) Content of 20° C. xylene-Soluble Portion (CXS) (Unit: % by Weight)

One gram of polymer composition was dissolved completely in 100 ml ofboiling xylene and then cooled to 20° C. After being left for fourhours, the mixture was separated by filtration into a solid and asolution. The filtrate was evaporated and was dried under reducedpressure at 70° C., yielding a dry solid. The dry solid was weighed andthen the content of 20° C. xylene-soluble portion (CXS) in the polymercomposition was determined.

(5) Melt Flow Rate (MFR; Unit: g/10 Minutes)

The MFR was determined according to JIS K 7210 at a temperature of 230°C. under a load of 21.18 N.

(6) Melting Point (Tm; Unit: ° C.)

A polymer composition was subjected to hot press molding includingoperations [1] through [5] shown below, yielding a sheet 0.5 mm inthickness.

[1] To introduce a mass of polymer composition into a molding sectioncontrolled to 230° C. in a compression molding machine manufactured byShinto Metal Industries, Ltd.

[2] To preheat the polymer composition to 230° C. in the molding sectionfor five minutes without application of load.

[3] To increase the pressure applied to the mass of polymer compositionup to 50 kgf/cm² in three minutes using a pressing machine.

[4] To keep the pressure at 50 kgf/cm² for two minutes.

[5] To transfer the sample obtained in step [4] above to a moldingsection controlled to 30° C. in another compression molding machinemanufactured by Shinto Metal Industries, Ltd. and to press the sampleunder a pressure of 30 kgf/cm² for five minutes.

Using a differential scanning calorimeter (Model DSC-7, manufactured byPerkinElmer Inc.), a 10 mg portion taken from the pressed sheet wassubjected to a thermal hysteresis including the operations (i) through(vii) shown below under a nitrogen atmosphere. During the step (vii), afusion curve was produced. In the resulting fusion curve, a temperature(° C.) where the highest endothermic curve appears was determined. Thetemperature was used as the melting point of the polymer composition.

(i) To heat a sample from room temperature to 220° C. at a rate of 300°C./min.

(ii) To hold the sample at 220° C. for five minutes.

(iii) To cool the sample from 200° C. to 150° C. at a rate of 300°C./min.

(iv) To hold the sample at 150° C. for one minute.

(v) To cool the sample from 150° C. to 50° C. at a rate 5° C./min.

(vi) To hold the sample at 50° C. for one minute.

(vii) To heat the sample from 50° C. to 180° C. at a rate of 5° C./min.

(7) Transparency (Haze; Unit: %)

The haze was measured according to JIS K 7105.

(8) Heat Seal Temperature (HST; Unit: ° C.)

Two pieces of the same film composed of a surface layer and a substratelayer were laminated in a manner that the surface layer of one piece wasput on the surface layer of the other piece. The laminated pieces werepressed under a load of 2 kgf/cm² for two seconds by means of a heatsealer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) heated to apredetermined temperature, thereby being heat sealed. The resultingsample was conditioned overnight at a temperature of 23° C. at ahumidity of 50%. Then, the sample was measured for a peel resistance bypeeling the laminated layers under the following conditions: atemperature of 23° C., a humidity of 50%, a peel speed of 200 mm/min anda peel angle of 180°. The heat sealing and the peel test were repeatedwhile the seal temperature was varied and a seal temperature at which apeel resistance of 300 g/25 mm was achieved was determined. The sealtemperature was used as the heat seal temperature (HST) of the film.

(9) Hot Tack Strength (HT; Unit: g/75 mm)

Two 75 mm-wide pieces of the same film composed of a surface layer and asubstrate layer were laminated in a manner that the surface layer of onepiece was put on the surface layer of the other piece. The laminatedpieces were pressed under a load of 2 kg/cm² for two seconds by means ofa heat sealer heated to a predetermined temperature, thereby being heatsealed. Just after the load was removed, a peel force was applied to thesealed portion using a leaf spring, thereby allowing the surface layersto peel from each other. The peel length was measured.

The peel test described above was repeated at different peel forcesusing leaf springs different in spring constant and a peel forceresulting in a peel length of 3.2 mm was determined. The springconstants of the leaf springs used were 53 g, 77 g, 110 g, 154 g, 224 g,250 g and 295 g.

(10) Tackiness of Film During its Formation

A film which had been biaxially stretched and then passed through anoven having a preheating section controlled to 175° C. and 165° C., astretching section controlled to 157° C. and a heat-setting sectioncontrolled to 165° C. was touched with fingers. When no tackiness wasfelt, the film was judged to be “good.” Conversely, when a much degreeof tackiness was felt, the film was judged to be “poor.”

Example 1

[Polymer (A-1)]

A solid catalyst was prepared and polymerization was carried out in thesame manner as Example 1 disclosed in JP-A-2002-069143. Thus, a powder(A) of a propylene-1-butene copolymer having a content of structuralunits derived from 1-butene of 24.6% by weight and an MFR of 2.2 g/10minutes was obtained. To 100 parts by weight of the resulting powder(A), 0.1 part by weight of calcium stearate, 0.05 part by weight ofIrganox 1010 (manufactured by Ciba Specialty Chemicals), 0.1 part byweight of 2,6-di-tert-butyl-4-methylphenol (BHT manufactured by SumitomoChemical Co., Ltd.), 0.4 part by weight of Tospearl 120 (manufactured byGE Toshiba Silicones) and 0.25 part by weight of an MFR regulator weremixed. The resulting mixture was melt kneaded at 220° C. and thenextruded through an extruder. The strand-shaped extrudate was cooled andcut. Thus, polymer (A-1) having an MFR of 10.3 g/10 minutes in the formof pellets was obtained. The MFR regulator used was a masterbatchcomposed of polypropylene powder impregnated with 8% by weight of2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[Polymer (B-1)]

TAFMER BL3080 (1-butene-ethylene copolymer manufactured by MitsuiChemicals, Inc.; [η]=2.56 dl/g, Tm=79° C.)

[Polymer Composition (1)]

Ninety percent by weight of the polymer (A-1) prepared above and 10% byweight of TAFMER BL3080 (i.e., polymer (B-1)) were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymercomposition (1) in the form of pellets was obtained. Polymer composition(1) had an MFR of 7.9 g/10 minutes and it contained CXS in an amount of28.3% by weight. The [η]CXS was 1.65 dl/g. The constitution, CXS and[η]CXS of polymer composition (1) are shown in Table 1.

[Preparation of Drawn Film]

A drawn film having a surface layer and a substrate layer was producedin the manner described below.

Polymer composition (1) prepared above was used for forming the surfacelayer. Polypropylene FS2011DG2 manufactured by Sumitomo Chemical Co.,Ltd. (melting point=159° C., MFR=2.5 g/10 minutes) was used for formingthe substrate layer. In separate extruders, polymer composition (1) andFS2011DG2 were melt kneaded separately at 230° C. and 260° C.,respectively, and then were charged into a coextrusion T die. Theextrudate having a two-kind two-layer structure, namely a surfacelayer/substrate layer structure, extruded through the T die was cooledrapidly to 30° C. and solidified on a chill roll. Thus, a cast sheet 1mm in thickness was obtained.

The resulting cast sheet was preheated and then was stretched five timesin the longitudinal direction at a stretching temperature of 145° C. bythe action of difference in peripheral speed between rolls of alongitudinal stretching machine. Subsequently, the sheet was stretchedeight times in the transverse direction at a stretching temperature of157° C. in an oven and then was subjected to heat treatment at 165° C.Thus, a biaxially drawn multilayer film having a layer constitution:surface layer/substrate layer=1 μm/20 μm was obtained. The film waswound up by a winding machine. Physical properties of the biaxiallydrawn multilayer film are shown in Table 2.

Example 2

[Polymer (A-2)]

To 100 parts by weight of powder (A) of the propylene-1-butene copolymerobtained in Example 1, 0.1 part by weight of calcium stearate, 0.05 partby weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals),0.1 part by weight of 2,6-di-tert-butyl-4-methylphenol (BHT manufacturedby Sumitomo Chemical Co., Ltd.), 0.4 part by weight of Tospearl 120(manufactured by GE Toshiba Silicones) and 0.22 part by weight of an MFRregulator the same as that used in Example 1 were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymer(A-2) having an MFR of 8.5 g/10 minutes in the form of pellets wasobtained.

[Polymer (B-2)]

TAFMER BL3110 (1-butene-ethylene copolymer manufactured by MitsuiChemicals, Inc.; [η]=1.79 dl/g, Tm=100.7° C.)

[Preparation of Polymer Composition (2) and Drawn Film]

Ninety percent by weight of the polymer (A-2) prepared above and 10% byweight of TAFMER BL3110 (polymer (B-2)) were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymercomposition (2) in the form of pellets was obtained. The polymercomposition (2) had an MFR of 8.6 g/10 minutes and it contained CXS inan amount of 28.2% by weight. The [η]CXS was 1.40 dl/g. Theconstitution, CXS and [η]CXS of polymer composition (2) are shown inTable 1.

A biaxially drawn multilayer film was produced in the same manner asExample 1 except the polymer composition (1) used for forming thesubstrate layer was changed to the polymer composition (2). Physicalproperties of the biaxially drawn multilayer film are shown in Table 2.

Comparative Example 1

[Polymer (A-3)]

To 100 parts by weight of powder (A) of the propylene-1-butene copolymerobtained in Example 1, 0.1 part by weight of calcium stearate, 0.05 partby weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals),0.1 part by weight of 2,6-di-tert-butyl-4-methylphenol (BHT manufacturedby Sumitomo Chemical Co., Ltd.), 0.4 part by weight of Tospearl 120(manufactured by GE Toshiba Silicones) and 0.21 part by weight of an MFRregulator the same as that used in Example 1 were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymer(A-3) having an MFR of 7.8 g/10 minutes in the form of pellets wasobtained.

[Polymer (B-3)]

TAFMER BL3450 (1-butene-ethylene copolymer manufactured by MitsuiChemicals, Inc.; [η]=1.35 dl/g, Tm=94.7° C.)

[Preparation of Polymer Composition (3) and Drawn Film]

Ninety percent by weight of the polymer (A-3) prepared above and 10% byweight of TAFMER BL3450 (i.e., polymer (B-3)) were mixed The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymercomposition (3) in the form of pellets was obtained. The polymercomposition (3) had an MFR of 8.3 g/10 minutes and it contained CXS inan amount of 28.2% by weight. The [η]CXS was 1.28 dl/g. Theconstitution, CXS and [η]CXS of polymer composition (2) are shown inTable 1.

A biaxially drawn multilayer film was produced in the same manner asExample 1 except the polymer composition (1) used for forming thesubstrate layer was changed to the polymer composition (3). Physicalproperties of the biaxially drawn multilayer film are shown in Table 2.TABLE 1 Polymer (A) Polymer (B) Content Content CXS [η]CXS Kind (%) Kind(%) (%) (dl/g) Example 1 A-1 90 B-1 10 28.3 1.65 Example 2 A-2 90 B-2 1028.2 1.40 Comparative A-3 90 B-3 10 28.2 1.28 Example 1

TABLE 2 HT(g/75 mm) Haze HST 90° 100° 110° 120° 130° 140° 150° (%) (°C.) C. C. C. C. C. C. C. Example 1 2.4 80 <53 130 197  295< 288 113 <53Example 2 2.5 81 <53 119 178 269 268 108 <53 Comparative 2.4 79 <53 108138 233 164 61 <53 Example 1

Examples 1 and 2, which satisfy the requirements of the presentinvention, are superior in low-temperature heat sealability, hot tackproperty and transparency.

Conversely, in Comparative Example 1, which does not satisfy one of therequirements of the present invention regarding the intrinsic viscosity([η]CXS) of 20° C. xylene-soluble portion of a polymer composition, aninsufficient hot tack strength was obtained.

Example 3

[Polymer (A-4)]

To 100 parts by weight of powder (A) of the propylene-1-butene copolymerobtained in Example 1, 0.1 part by weight of calcium stearate, 0.05 partby weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals),0.1 part by weight of 2,6-di-tert-butyl-4-methylphenol (BHT manufacturedby Sumitomo Chemical Co., Ltd.), 0.4 part by weight of Tospearl 120(manufactured by GE Toshiba Silicones) and 0.21 part by weight of an MFRregulator the same as that used in Example 1 were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymer(A-4) having an MFR of 7.9 g/10 minutes in the form of pellets wasobtained.

[Polymer (B-1)]

TAFMER BL3080 (1-butene-ethylene copolymer manufactured by MitsuiChemicals, Inc.; [η]=2.56 dl/g, Tm=79° C.)

[Polymer (D-1)]

Propylene homopolymer (Tm=164° C., MFR=140 g/10 minutes)

[Polymer Composition (4)]

Eighty-five parts by weight of the polymer (A-4) prepared above, 10parts by weight of TAFMER BL3080 (i.e., polymer (B-1)) and 5 parts byweight of the aforementioned polymer (D-1) were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymercomposition (4) in the form of pellets was obtained.

In the resulting polymer composition (4), the proportions of polymer(A-4) and polymer (B-1) were 89.5% by weight and 10.5% by weight,respectively. The content, based on 100 parts by weight of polymers(A-4) and (B-1) in total, of polymer (D-1) was 5.26 parts by weight.

Polymer composition (4) had an MFR of 6.3 g/10 minutes and it containedCXS in an amount of 25.0% by weight. The [η]CXS was 1.77 dl/g. Theconstitution, CXS and [η]CXS of polymer composition (4) are shown inTable 3.

[Preparation of Drawn Film]

A drawn film having a surface layer and a substrate layer was producedin the manner described below. Polymer composition (4) prepared abovewas used for forming the surface layer. Polypropylene FS2011DG2manufactured by Sumitomo Chemical Co., Ltd. (melting point=159° C.,MFR=2.5 g/10 minutes) was used for forming the substrate layer. Polymercomposition (4) and FS2011DG2 were melt kneaded separately in separateextruders, and then were charged into a coextrusion T die. The extrudatehaving a two-kind two-layer structure, namely a surface layer/substratelayer structure, extruded through the T die was cooled rapidly to 30° C.and solidified on a chill roll. Thus, a cast sheet 1 mm in thickness wasobtained.

The resulting cast sheet was preheated and then was stretched five timesin the longitudinal direction at a stretching temperature of 145° C. bythe action of difference in peripheral speed between rolls of alongitudinal stretching machine. Subsequently, the sheet was stretchedeight times in the transverse direction at a stretching temperature of157° C. in an oven and then was subjected to heat treatment at 165° C.Thus, a biaxially drawn multilayer film having a layer constitution:surface layer/substrate layer=1 μm/20 μm was obtained. The film waswound up by a winding machine. Physical properties of the biaxiallydrawn multilayer film are shown in Table 4.

Example 4

[Polymer (A-5)]

To 100 parts by weight of powder (A) of the propylene-1-butene copolymerobtained in Example 1, 0.1 part by weight of calcium stearate, 0.05 partby weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals),0.1 part by weight of 2,6-di-tert-butyl-4-methylphenol (BHT manufacturedby Sumitomo Chemical Co., Ltd.), 0.4 part by weight of Tospearl 120(manufactured by GE Toshiba Silicones) and 0.21 part by weight of an MFRregulator the same as that used in Example 1 were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymer(A-5) having an MFR of 7.9 g/10 minutes in the form of pellets wasobtained.

[Polymer (B-2)]

TAFMER BL3110 (1-butene-ethylene copolymer manufactured by MitsuiChemicals, Inc.; [η]=1.79 dl/g, Tm=100.7° C.)

[Preparation of Polymer Composition (5) and Drawn Film]

Eighty-five percent by weight of the polymer (A-5) prepared above, 10parts by weight of TAFMER BL3110 (i.e., polymer (B-2)) and 5 parts byweight of the aforementioned polymer (D-1) were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymercomposition (5) in the form of pellets was obtained.

In the resulting polymer composition (5), the proportions of polymer(A-5) and polymer (B-2) were 89.5% by weight and 10.5% by weight,respectively. The content, based on 100 parts by weight of polymers(A-5) and (B-2) in total, of polymer (D-1) was 5.26 parts by weight.

The polymer composition (5) had an MFR of 7.8 g/10 minutes and itcontained CXS in an amount of 23.7% by weight. The [η]CXS was 1.44 dl/g.The constitution, CXS and [η]CXS of polymer composition (5) are shown inTable 3.

A biaxially drawn multilayer film was produced in the same manner asExample 3 except the polymer composition (4) used for forming thesubstrate layer was changed to the polymer composition (5). Physicalproperties of the biaxially drawn multilayer film are shown in Table 4.

Example 5

[Polymer (C-1)]

To 100 parts by weight of propylene-ethylene-1-butene copolymer (contentof structural units derived from ethylene=4.0% by weight, content ofstructural units derived from 1-butene=3.6% by weight, Tm-129° C.,MFR=6.0 g/10 minutes), 0.1 part by weight of calcium stearate, 0.05 partby weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals),0.1 part by weight of 2,6-di-tert-butyl-4-methylphenol (BHT manufacturedby Sumitomo Chemical Co., Ltd.), 0.4 part by weight of Tospearl 120(manufactured by GE Toshiba Silicones) and 0.75 part by weight of an MFRregulator the same as that used in Example 1 were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymer(C-1) having an MFR of 44 g/10 minutes in the form of pellets wasobtained.

[Preparation of Polymer Composition (6) and Drawn Film]

Thirty percent by weight of the polymer (C-1) prepared above, 10 partsby weight of TAFMER BL3080 (i.e., polymer (B-1), 5 parts by weight ofpolymer (D-1), 55 parts by weight of powder (A) of thepropylene-1-butene copolymer used in Example 1 and moreover, based on100 parts by weight of these four components in total, 0.055 part byweight of calcium stearate, 0.0275 part by weight of Irganox 1010(manufactured by Ciba Specialty Chemicals), 0.055 part by weight of2,6-di-tert-butyl-4-methylphenol (BHT manufactured by Sumitomo ChemicalCo., Ltd.) and 0.22 part by weight of Tospearl 120 (manufactured by GEToshiba Silicones) were mixed. The resulting mixture was melt kneaded at220° C. and then extruded through an extruder. The strand-shapedextrudate was cooled and cut. Thus, polymer composition (6) in the formof pellets was obtained.

In the resulting polymer composition (6), the proportions of powder (A),polymer (B-1) and polymer (C-1) were 57.9% by weight, 10.5% by weightand 31.6% by weight, respectively. Moreover, the content of polymer(D-1) was 5.26 parts by weight based on 100 parts by weight of powder(A), polymer (B-1) and polymer (C-1) in total.

The polymer composition (6) had an MFR of 6.4 g/10 minutes and itcontained CXS in an amount of 22.8% by weight. The [η]CXS was 1.69 dl/g.The constitution, CXS and [η]CXS of polymer composition (6) are shown inTable 3.

A biaxially drawn multilayer film was produced in the same manner asExample 3 except the polymer composition (4) used for forming thesubstrate layer was changed to the polymer composition (6). Physicalproperties of the biaxially drawn multilayer film are shown in Table 4.

Comparative Example 2

[Polymer (B-3)]

TAFMER BL3450 (1-butene-ethylene copolymer manufactured by MitsuiChemicals, Inc.; [η]=1.35 dl/g, Tm=94.7° C.)

[Preparation of Polymer Composition (7) and Drawn Film]

To 90 parts by weight of powder (A) of the propylene-1-butene copolymerobtained in Example 1 and 10 parts by weight of TAFMER BL3450 (i.e.,polymer (B-3)), 0.1 part by weight of calcium stearate, 0.05 part byweight of Irganox 1010 (manufactured by Ciba Specialty Chemicals), 0.1part by weight of 2,6-di-tert-butyl-4-methylphenol (BHT manufactured bySumitomo Chemical Co., Ltd.), 0.4 part by weight of Tospearl 120(manufactured by GE Toshiba Silicones) and 0.12 part by weight of an MFRregulator the same as that used in Example 1 were mixed. The resultingmixture was melt kneaded at 220° C. and then extruded through anextruder. The strand-shaped extrudate was cooled and cut. Thus, polymercomposition (7) in the form of pellets was obtained.

In the resulting polymer composition (7), the proportions of powder (A)and polymer (B-3) were 90% by weight and 10% by weight, respectively.

The polymer composition (7) had an MFR of 8.7 g/10 minutes and itcontained CXS in an amount of 27.8% by weight. The [η]CXS was 1.19 d/g.The constitution, CXS and [η]CXS of polymer composition (7) are shown inTable 3.

A biaxially drawn multilayer film was produced in the same manner asExample 3 except the polymer composition (4) used for forming thesubstrate layer was changed to the polymer composition (7). Physicalproperties of the biaxially drawn multilayer film are shown in Table 4.

Comparative Example 3

[Polymer Composition (8)]

To 85 parts by weight of powder (A) of the propylene-1-butene copolymerobtained in Example 1, 10 parts by weight of TAFMER BL3450 (polymer(B-3)) and 5 parts by weight of polymer (D-1), 0 1 part by weight ofcalcium stearate, 0.05 part by weight of Irganox 1010 (manufactured byCiba Specialty Chemicals), 0.1 part by weight of2,6-di-tert-butyl-4-methylphenol (BHT manufactured by Sumitomo ChemicalCo., Ltd.), 0.4 part by weight of Tospearl 120 (manufactured by GEToshiba Silicones) and 0.11 part by weight of an MFR regulator the sameas that used in Example 1 were mixed. The resulting mixture was meltkneaded at 220° C. and then extruded through an extruder. Thestrand-shaped extrudate was cooled and cut. Thus, polymer composition(8) in the form of pellets was obtained.

In the resulting polymer composition (8), the proportions of powder (A)and polymer (B-3) were 89.5% by weight and 10.5% by weight,respectively. Moreover, the content of polymer (D-1) was 5.26 parts byweight based on 100 parts by weight of powder (A) and polymer (B-3) intotal.

The polymer composition (8) had an MFR of 6.8 g/10 minutes and itcontained CXS in an amount of 24.5% by weight. The [η]CXS was 1.21 dl/g.The constitution, CXS and [η]CXS of polymer composition (8) are shown inTable 3.

A biaxially drawn multilayer film was produced in the same manner asExample 3 except the polymer composition (4) used for forming thesubstrate layer was changed to the polymer composition (8). Physicalproperties of the biaxially drawn multilayer film are shown in Table 4.TABLE 3 Polymer Polymer Polymer (A) Polymer (B) (D-1) (C-1) ContentContent Content Content CXS [η]CXS Kind (%) Kind (%) (%) (%) (%) (dl/g)Example 3 A-4 85 B-1 10 5 0 25.0 1.77 Example 4 A-5 85 B-2 10 5 0 23.71.44 Example 5 Powder 55 B-1 10 5 30 22.8 1.69 (A) Coraparative Powder90 B-3 10 0 0 27.8 1.19 Example 2 (A) Comparative Powder 85 B-3 10 5 024.5 1.21 Example 3 (A)

TABLE 4 HT(g/75 mm) Haze HST 90° 100° 110° 120° 130° 140° 150° (%) (°C.) C. C. C. C. C. C. C. Tackiness Example 3 2.5 84 <53 120 157 160 178107 <53 good Example 4 2.6 85 <53 90 113 116 113 73 <53 good Example 52.8 85 <53 60 104 131 185 94 <53 good Comparative 2.5 81 <53 75 68 196158 67 <53 poor Example 2 Comparative 2.9 84 <53 53 53 53 113 71 <53good Example 3

Examples 3 through 5, which satisfy the requirements of the presentinvention, are superior in low-temperature heat sealability, hot tackproperty and transparency tackiness was not recognized.

Conversely, in Comparative Example 2, which does not contain polymer (D)that is one of the requirements of the present invention, a much degreeof tackiness was recognized. In Comparative Example 1, which does notsatisfy one of the requirements of the present invention regarding theintrinsic viscosity ([η]CXS) of 20° C. xylene-soluble portion of apolymer composition, an insufficient hot tack strength was obtained.

As described in detail above, according to the present invention, onecan obtain a polymer composition from which a film superior inlow-temperature heat sealability, hot tack property and transparency canbe afforded and also can obtain a film thereof. In addition, accordingto the present invention, one can obtain a polymer composition fromwhich films superior in low-temperature heat sealability, hot tackproperty and transparency can be obtained and which exhibit lesstackiness when being fabricated into films can be afforded and also onecan obtain a film thereof.

1. A polymer composition comprising: from 30 to 98% by weight of a polymer (A) satisfying Requirements (A-1) through (A-3) defined below, from 1 to 30% by weight of a polymer (B) satisfying Requirements (B-1) and (B-2) defined below, and from 1 to 50% by weight of a polymer (C) satisfying Requirements (C-1) through (C-5), the polymer composition satisfying Requirements (1) and (2) defined below, wherein said amounts of the polymers (A), (B) and (C) are based on a combined amount of the polymers (A), (B) and (C): Requirement (1): the content of a 20° C. xylene-soluble portion of the polymer composition is from 5 to 45% by weight, Requirement (2): a 20° C. xylene-soluble portion of the polymer composition has an intrinsic viscosity of 1.3 dl/g or higher, Requirement (A-1): the polymer is a copolymer of propylene and α-olefin having 4 or more carbon atoms or a copolymer of propylene, α-olefin having 4 or more carbon atoms and ethylene, Requirement (A-2): the polymer has a content of structural units derived from α-olefin having 4 or more carbon atoms of from 3 to 40% by weight, Requirement (A-3): the polymer has a content of structural units derived from ethylene of from 0.1 to 5% by weight when the polymer is a copolymer of propylene, α-olefin having 4 or more carbon atoms and ethylene, Requirement (B-1): the polymer is a homopolymer of 1-butene, a copolymer of 1-butene and ethylene, a copolymer of 1-butene and propylene, a copolymer of 1-butene and α-olefin having 4 or more carbon atoms other than 1-butene, a copolymer of 1-butene, ethylene and propylene or a copolymer of 1-butene, ethylene and α-olefin having 4 or more carbon atoms other than 1-butene, Requirement (B-2): the polymer has a melting point of not lower than 60° C. but lower than 125° C., Requirement (C-1): the polymer is a copolymer of propylene and ethylene, a copolymer propylene and α-olefin having 4 or more carbon atoms, or a copolymer of propylene, ethylene and α-olefin having 4 or more carbon atoms, Requirement (C-2): the polymer has a content of structural units derived from ethylene of from 0 1 to 10% by weight when the polymer is a copolymer of propylene and ethylene or a copolymer of propylene, ethylene and α-olefin having 4 or more carbon atoms, wherein this content is based on the weight of the polymer, Requirement (C-3): the polymer has a content of structural units derived from α-olefin having 4 or more carbon atoms of from 0.1 to 10% by weight when the polymer is a copolymer of propylene and α-olefin having 4 or more carbon atoms or a copolymer of propylene, ethylene and α-olefin having 4 or more carbon atoms, Requirement (C-4): the polymer has a content, based on the weight of the polymer, of structural units derived from α-olefin having 4 or more carbon atoms less than that of polymer (A) when the polymer is a copolymer of propylene and α-olefin having 4 or more carbon atoms or a copolymer of propylene, ethylene and α-olefin having 4 or more carbon atoms, and Requirement (C-5): the polymer has a melting point of not lower than 125° C. but lower than 150° C.
 2. The polymer composition according to claim 1, wherein the polymer composition further comprises from 1 to 25 parts by weight, based on 100 parts by weight of the polymers (A), (B) and (C) in total, of a polymer (D) satisfying Requirements (D-1), (D-2) and (D-3) defined below: Requirement (D-1): the polymer is a homopolymer of propylene, a copolymer of propylene and ethylene or a copolymer of propylene and α-olefin having 4 or more carbon atoms, Requirement (D-2): the polymer has a melting point of from 150° C. to 170° C., and Requirement (D-3): the polymer has a content of structural units derived from ethylene of from 0.1 to 3% by weight when the polymer is a copolymer of propylene and ethylene or the polymer has a content of structural units derived from α-olefin having 4 or more carbon atoms of from 0.1 to 3% by weight when the polymer is a copolymer of propylene and α-olefin having 4 or more carbon atoms.
 3. The polymer composition according to claim 1 or 2, wherein the polymer (A) is a copolymer of propylene and 1-butene.
 4. The polymer composition according to claim 1 or 2, wherein the polymer (C) is a copolymer of propylene and ethylene or a copolymer of propylene, ethylene and 1-butene.
 5. The polymer composition according to claim 2, wherein the polymer (D) is a homopolymer of propylene having a melting point of from 155° C. to 170° C.
 6. A film having at least one layer made of the polymer composition according to claim
 1. 